Electrocatalysis最新文献

The research focuses on creating an innovative graphitic carbon nitride electrochemical sensor (g-C₃N₄) for the precise and sensitive detection of the antiviral medication valganciclovir (VCR), also known as Valcyte. VCR is an antiviral medication used to treat diseases, including CMV retinitis, and to protect transplant patients against CMV infection by stopping the virus from spreading. This drug is typically given to patients with weak immune systems, HIV/AIDS, and organ transplants. Though VCR provides numerous benefits, it must be administered with caution as it can cause allergic reactions and renal damage. A modified carbon paste electrode called g-C₃N₄/CPE has demonstrated remarkable electrocatalytic activity in oxidizing varying levels of chlorine radiation. Various methods were employed to characterize the created g-C₃N₄, including field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and Raman and Fourier transform infrared (FT-IR). The sensor has a detection range of 1 to 16 µM, which makes it more sensitive than traditional drug detection techniques. It can detect as low as 0.88 × 10⁻⁸ M under ideal experimental conditions. The sensor’s ability to identify VCR using g-C₃N₄ was tested using amperometric i-t curve analysis. The EIS (electrochemical impedance spectroscopy) was employed to investigate the electrochemical features of many electrodes. The comparable R_ct values were 3114 Ω, 13,770 Ω, and 3794 Ω for g-C₃N₄/CPE, bare GCE, and bare CPE, respectively. During the test, various commonly used interferents and drugs were introduced to the VCR solution to examine the influence of foreign interferents on the outcomes. Various electrokinetic factors were examined to explore the electrochemical behavior of VCR. Environmental monitoring, drug analysis, and clinical diagnostics benefited from successfully using the generated g-C₃N₄/CPE. Additionally, it can play a vital role in creating new and efficient methods for antiviral drug VCR determination.

Graphical Abstract

A composite containing silver nanoparticles embedded Mn-MOFs has been synthesized using a simple solvothermal route. The composite-modified electrode has been utilized in the simultaneous measurement of purine base pairs of DNA [guanine (GU), adenine (AD)] and uric acid (UA). The morphology of the composite has been studied by scanning electron microscopy which revealed that the Ag nanoparticles homogeneously get distributed over the layers of Mn-MOFs. The thermal stability of the composite has been studied by thermogravimetric analysis. BET adsorption–desorption isotherm study revealed the large surface area and mesoporous nature of the composite. The electrochemical behavior of the composite material has been studied through impedance spectroscopy, cyclic voltammetry (CV), and square wave voltammetry (SWV) techniques to decipher the redox nature of it towards the target analytes like GU, AD, and UA. Each of these analytes has displayed a distinct catalytic oxidative signal with well-resolved peaks during their simultaneous measurement. The linearity obtained for UA, GU, and AD by square wave voltammetry is in the concentration range of 0.5–280 µM with a limit of detection of 64.49, 78.84, and 125.33 nM, respectively. The composite-modified electrode has been successfully applied to real sample matrices like human serum, urine, and commercially available fish sperm DNA samples. The fabricated sensor showed very good responses to these analytes from real sample matrices with prolonged stability and reproducibility.

Graphical Abstract

It is of key importance to design efficient insulin electrocatalysts based on nonprecious noble metal-free. However, the design of advanced nanostructured based metal phosphides is scarcely reported. In this work, for the first time, a novel insulin sensor based on Ni₂P electrode materials with nanoplate structure was designed. In this regard, Hofmann-type coordination polymers (HCPs) based on Ni(H₂O)₂[Ni(CN)₄]·H₂O (Ni–Ni HCP) were prepared and used as precursors to the preparation of Ni₂P. The unique layer structure of Ni–Ni HCP precursors can lead to the preparation of Ni₂P nanoplates with large surface areas, high availability of active catalytic centers, and abundant interior space for fast diffusion and boosted reaction kinetics. The electrochemical results showed that the Ni₂P nanoplates offer excellent capability toward insulin oxidation in 0.1 M NaOH electrolyte solution. Moreover, a proper linear relationship was obtained between insulin concentrations and the current responses in the range of 10 to 100 pM with the detection limit of 3 pM and with good capability for the determination of insulin in the human blood serum sample. This work offers a rational method for the structure engineering of Ni₂P nanoplates using HCP precursors, which can lead to the fabrication of high-performance insulin sensor.

Graphical Abstract

In situ synthesis of novel hybrid organic–inorganic nanopetals (HNPs) of Copper (Cu²⁺) and gold-conjugated hemoglobin (Au@Hb) is reported. The presence of Au within the protein matrix prevents the formation of a flower-like assembly of the formed nanopetals of Au@Hb and Cu²⁺ via the co-precipitation method. Morphological, chemical, and electrocatalytic activities of in situ synthesized Au@Hb-Cu HNPs were examined systematically. The hybrid nanopetal (Au@Hb-Cu HNP)-modified screen-printed PET electrodes show enhanced electrocatalytic activity toward the oxidation of H₂O₂ compared to electrodes modified with Hb-copper hybrid nanoflowers (Hb-Cu HNFs) without Au conjugation. The proposed biosensor exhibits excellent electrochemical performance with broad linear responses over a H₂O₂ concentration ranging from 5 to 1000 µM (R² = 0.99) and showed a lower detection limit of 1.46 µM at 0.30 V vs. pseudo Ag/AgCl. Enhanced electrochemical performance is attributed to heterogeneous active sites over hybrid nanopetal surfaces. Moreover, the hybrid nanopetal–modified electrodes showed excellent stability and anti-interference performance in the presence of ascorbic acid, uric acid, fructose, and glucose. These results demonstrate that Au@Hb-Cu HNPs offer a better and more promising alternative for the electrochemical detection of H₂O₂ sensitively.

Graphical Abstract

Abstract

A rational catalyst for electrocatalytic hydrogen evolution reaction (HER) is a long-standing challenge that researchers are confronted with. In view of this, tiny particles of transition metals (TMs) spread over a substrate acting as an active site for the reaction, scientifically known as single-atom catalysts is seen as an efficacious way for designing an efficient catalyst. Herein, we comprehensively investigated catalytic activity of Ni-atoms spread over various kinds of two-dimensional (2D) substrates like graphene, AlC, AlN, h-BN, BeO, and MgO (Ni@2D) towards HER using density functional theory calculations. All the considered 2D substrates have various inequivalent anchoring sites like top, hollow, bridge, and vacancy sites for Ni-atoms. So, there are total 34 anchoring sites, and we computed binding energy (E(_b)) of Ni-atom over all the sites. Having large number of configurations, we first applied a screener on stability of Ni@2D and only considered those configurations for which the E(_b) value is <(-)3.00 eV for further calculations. Out of 34, 17 configurations were falling in this range. Further, we computed the differential Gibbs free energy of H-adsorption ((Delta)G(_H)) and generated volcano plot between (Delta)G(_H) and exchange current density ((i_0)) as a prime indicators of HER activity. Then, we screened these configurations based on (Delta)G(_H) values that (|Delta)G(_H|) (le) to 0.5 eV, and out of 17, 10 systems were falling in this region. At last, we examined complete reaction profile of HER via Volmer-Heyrovsky (VH) and Volmer-Tafel (VT) mechanisms over the remaining 10 configurations, and the lowest activation energy for HER are 0.12 eV and 0.21 eV for Ni@AlN and 0.28 eV and 0.36 eV for Ni@h-BN via VT and VH mechanism, respectively. Our findings show Ni@AlN and Ni@h-BN could be a non-noble TM candidate for eco-operational HER catalyst.

Graphical Abstract

CoSe is one of the chalcogenides attracting much attention due to its excellent hydrogen evolution reaction (HER) activity and low price. However, CoSe prepared by electrodeposition generally shows lower HER activity and stability under acidic conditions than those prepared by other methods. In this study, it was assumed that the cause of the low HER performance of electrodeposited CoSe is mainly due to the dissolution of Co and Se, which do not form a stable alloy, and annealing of electrodeposited CoSe was introduced to demonstrate this. We compared the HER activity and stability of non-annealed and annealed CoSe in 0.5 M H₂SO₄ electrolyte and investigated the dissolution behaviors of the two catalysts during HER. As a result, it was found that Co and Se, which did not form a stoichiometric CoSe₂ alloy, were found to be vulnerable in acidic conditions. The annealing induced additional CoSe₂ formation, improving the HER activity and stability of electrodeposited CoSe. The annealed CoSe exhibited an overpotential of 175 mV at 10 mA cm⁻², 27 mV lower than that of non-annealed one, and was stable for 48 h at 10 mA cm⁻².

Graphical Abstract

Different morphology metal nickel nanoelectrodes, such as nanospikes, layered nanosheets, layered flat particles, and hierarchical nanosheets, were synthesized on FTO glass via a hydrothermal method and utilized for glucose concentration determination in aqueous solutions under alkaline conditions. These electrodes demonstrated distinct electrochemical catalytic properties, such as surface area, mass transfer, and catalytic rate, during the glucose oxidation process. It was observed that a larger surface area can lead to a higher redox current in the absence of glucose, along with increased current noise and a prolonged response time when glucose is present. Despite having similar surface coverage, electrodes with a larger surface area can accommodate more Ni²⁺/Ni³⁺ redox couples, which generate a higher redox current in an alkaline solution. However, a poor catalytic rate for glucose can result in a low sensitivity of glucose detection. This implies that not all redox couples on the electrode surface actively participate in glucose oxidation, even when the electrodes have extensive glucose coverage and a higher density of redox couples. Moreover, a larger surface area can impede glucose diffusion, resulting in a longer response time during amperometric detection.

Graphical Abstract

The spinel CuFe₂O₄ elaborated by sol–gel route crystallizes in a tetragonal structure with a crystallite size of 444 ± 2 nm and a zeta potential of − 35 mV. The diffuse reflectance spectroscopy and photo-electrochemistry were undertaken for its characterization. The direct gap (1.55 eV) ideal for the solar energy conversion is assigned to the transition (: {Fe}_{oc}^{3+}:{t}_{2g}to {Fe}_{oc}^{4+}): ({e}_{g}) in agreement with the red color, allowing more than half of the solar spectrum to be converted into chemical energy. The narrow valence band deriving from Fe³⁺: ({t}_{2g}) orbital induces a low electron mobility (µ = 8.91 × 10⁻¹³ cm² V⁻¹ s⁻¹). The cyclic voltammetry in Na₂SO₄ (10⁻² M) exhibits low hysteresis that resembles a chemical diode. The electrical conductivity of CuFe₂O₄ is a characteristic of a non-degenerate semiconductor with activation energy (E_a) of 0.20 eV where the electron transfer occurs by low lattice polaron hopping between mixed valences Fe⁴⁺/Fe³⁺ octahedrally coordinated. The semi-logarithmic plot (logJ–E) indicates a chemical stability of CuFe₂O₄, while the photo-chronoamperometry corroborates the p-type behavior, a result confirmed by the capacitance measurement where an electron density (N_A) of 0.176 × 10²³ cm⁻³ and a flat band potential (E_fb) equal to − 0.56 V_SCE were extracted. As application and on the basis of the potential diagram, Rhodamine B (Rh B, 20 mg L⁻¹), a cationic dye, is electrostatically attracted by the electrode surface and successfully oxidized by electrocatalysis on CuFe₂O₄. The kinetics of oxidation of Rh B followed by chemical oxygen demand (COD) analysis, which gave an abatement of 56% under a current of 150 mA, an enhancement up to 70%, was reached by electro-photocatalysis under sunlight smaller than that analyzed by UV–visible spectrophotometry (88%). The color removal follows a pseudo-first-order model with a half-life t_1/2 of 57 min; a reaction mechanism by O₂^•− and ^•OH radicals is suggested.

Graphical Abstract